1. Field of the Invention
The present invention relates to an additional frame configuration for transmission in a significantly low signal-to-noise ratio (SNR) environment in digital video broadcasting-satellite second generation (DVB-S2) standard based transmission.
2. Description of the Related Art
A conventional digital video broadcasting-satellite second generation (DVB-S2) transmission system may perform transmission suitable for a channel environment in the signal-to-noise ratio (SNR) range of about 2.35 dB to about 16 dB as shown in a table 100 of FIG. 1. However, in the case of satellite communication, due to a rainfall environment and a difficulty coming from antenna installation, an SNR may be significantly low. In addition, a mobile terminal, when transmitting a high SNR signal, it may cause interference in a neighboring channel due to an antenna pointing error. Accordingly, when transmitting and receiving a satellite signal, there is a need to transmit a significantly low SNR signal. In the case of a current DVB-S2 standard, a new framework may not be performed since a large number of transmitters and receivers are already installed. Accordingly, a frame configuration not affecting existing equipment may be required.
A band spreading technology may be employed. The existing band spreading technology requires a separate apparatus for a band spreading function and thus, a receiver that does not support the band spreading function may have a difficulty in receiving data.
In general, the satellite communication may operate using a fixed bandwidth. The band spreading technology generally refers to a technology of spreading a bandwidth of a signal in order to transmit low signal power. A plurality of methods may be employed to spread the bandwidth, for example, a technology of repeatedly transmitting the same data and combining the data in a reception end to thereby enhance signal strength.
Accordingly, to simultaneously employ the band spreading technology and a technology not spreading a band, an amount of data of a signal of which a band is to be spread from a fixed bandwidth needs to be decreased. In this case, when an amount of data decreases due to a DVB-S2 form, many dummy frames may occur. Based on the above concept, a dummy frame may be substituted to be in a form in which an existing signal frame is repeated.
Generally, the band spreading technology may predict a temporal symbol repetition technology, a frame repetition technology, and a frequency repetition technology.
The frequency repetition technology employs a nonlinear amplifier for the satellite communication and thus, inter-modulation distortion occurs. Accordingly, it is difficult to apply a multi-carrier technology.
The symbol repetition technology is generally known as a direct-sequence (DS) band spreading technology. However, an existing DVB-S2 receiver may not receive such signal waveform.
In the case of the frame repetition technology, reception becomes impossible in a low SNR environment.
When performing synchronous accumulation of the respective received signals, the reception may become possible. However, in the case of an adaptive coding and modulation (ACM) technology employed in DVB-S2, a frame length varies and thus, it may be impossible to perform the synchronous accumulation.